[Pd] Stack Overflow

[Frank Barknecht]

Hallo,
Chuckk Hubbard hat gesagt: // Chuckk Hubbard wrote:

> This still doesn't make sense to me.  Anything coming from the
> second outlet of the pointer should be discarded, and the until
> ought to keep moving the pointer forward until something comes from
> either the first or third outlet.  If the 2nd outlet stopped the
> [until], there would be no point having the patch, and if it is
> connected to a [next( message, as it was before, it could lead to a
> stack overflow, as message after message triggers that outlet when
> searching for a single tempo marker among hundreds of notes.

Ah, yes, of course you're right here, I somehow did get this wrong,
bad coffee for breakfast. :(

I'll try again - this is from your previous mail:

> But I don't understand why the attached patch doesn't work.  Using
> my recursive patch, I get no "empty pointer" errors, no matter what
> I do in the program, from the abstraction.  However, this [until]
> version freezes my system, and the only way that would seem to be
> possible is if a "next" message were sent without a "bang" message
> having been sent first.

If you send a "next" before you send a "bang" to "JInextB", you get a
stack overflow. But you *also* get a stack overflow, if you send a
"next" *after* you have reached the end of the structures list.

You get this because there is nothing stopping the until: Instead of a
pointer out of the first or a bang out of the End_Of_List outlet of
the pointer object, you just get a console messages saying: 

error: ptrobj_next: no current pointer

You can check this yourself if you replace the [until] with a [bang]
message and press [next( manually until you reach the end of the list,
then press [next( again. There will be no output to any of the two
outlets of [JInextB], so there will be nothing to stop the [until]
(which thankfully only is a [bang] now).

The patch I posted earlier does fix this, as it's not the incoming
message, that starts the [until] loop, but anything, that is:

a) not a wanted pointer of type $1 and
b) not the end of the list. 

And this thing, that is "not a and not b", is a pointer from the
second (middle) outlet. 

Ciao
-- 
 Frank Barknecht                 _ ______footils.org_ __goto10.org__